[. . . ] A 6" (15. 2 cm) round vent system is needed for installation (not included). Flexible vent creates back pressure and air turbulence that greatly reduce performance. [. . . ] Flexible vent creates back pressure and air turbulence that greatly reduce performance. Rear discharge A 90° elbow may be installed immediately above the hood. Roof Venting Wall Venting LOCATION REQUIREMENTS Have a qualified technician install the range hood. It is the installer's responsibility to comply with installation clearances specified on the model/serial rating plate. The model/serial rating plate is located behind the left filter on the rear wall of the vent hood. 6" (15. 2 cm) min. * 6/" (16. 8 cm) *NOTE: The range hood chimneys are adjustable and designed to meet varying ceiling or soffit heights depending on the distance "X" between the bottom of the range hood and the cooking surface. For higher ceilings, a Stainless Steel Chimney Extension Kit Part Number W10337357 is available from your dealer or an authorized parts distributor. The chimney extension replaces the upper chimney shipped with the range hood. IMPORTANT: Minimum distance "X": 24" (61. 0 cm) from electric cooking surface. Minimum distance "X": 27" (68. 6 cm) from gas cooking surfaces. [. . . ] IMPORTANT: Minimum distance "X": 24" (61. 0 cm) from electric cooking surface. Minimum distance "X": 27" (68. 6 cm) from gas cooking surfaces. [. . . ]